This invention concerns an ignition rail for contacting an ignition device with the spark plugs of an internal combustion engine.
When using an ignition rail, spark plugs are not contacted to the ignition current via individual ignition cables complete with connector portions but all spark plugs of a cylinder head will be contacted jointly. The ignition rail consists of a tube portion carrier in which tube portions are mounted by means of connector portions. With this type of mounting, the ignition rail is removed whenever spark plugs need to be serviced; in this way all spark plugs for a cylinder head become accessible.
Within a cavity of the tube portion carrier parts of the ignition device can be arranged, which achieves particularly short connections between spark plug and ignition device.
For instance, an ignition rail is known from printed publication U.S. Pat. No. 4,903,675 where tube portions and connector portions are designed as joint parts. Tube portions each contain a primary coil by means of which the ignition voltage is transmitted contactless to specially designed spark plugs each of which contains a secondary coil.
The problem in the use of an ignition rail are unavoidable tolerances concerning the relative distances between the spark plugs which need to be compensated by the ignition rail. The ignition rail must be protected against the ingress of humidity.
In printed publication U.S. Pat. No. 5,577,921 a connection system for the electric connection of a spark plug according to the single coil concept is proposed. Here, a separate coil is mounted in the head component of each tube portion. At the end of the tube portion a connector portion is screwed on which is designed for conventional spark plugs. Protection against the ingress of humidity is ensured by O-rings.
The disadvantage of the plug-in type device consists in the complicated design of the connector portion as well as in the specially designed cylinder head for this plug-in type device, which only allows very low production tolerances.
Printed publication DE 39 20 080 A1 also describes an ignition device according to the single coil concept, where the ignition coil for a spark plug is located in a separate housing next to the tube portion with the connector portion. With this arrangement, the tube portions with the connector portions can be pulled off individually from the spark plugs without the ignition rail--which is designed as a housing encompassing the tube portions and the connector portions--having to be removed. Mounting the tube portions with the connector portions on the ignition rail is effected by means of a plug-in device which is implemented--for instance--as a bayonet catch.
The disadvantage of this ignition device lies in its complex and cost-intensive structural setup as well as in its decidedly high space requirement.